[codeconsole]

A method pointer assigned to or returned as a functional interface has its return type checked since GROOVY-12623, against the common type of every overload of the name. So an overloaded method that works on 6.0.0 no longer compiles on master:

@groovy.transform.CompileStatic
class C {
    Function<Integer,Integer> f() { Math.&abs }                 // Possible loss of precision from double to java.lang.Integer
    BiFunction<Integer,Integer,Integer> g() { Math.&max }       // same
}

An Integer argument selects abs(int) and max(int,int) at run time, so abs(double) should not count.

The check now uses the methods that values of the functional interface's parameter types can select: the best match for those types, and any method with narrower parameter types, which a value of a subtype selects. ToIntFunction<Object> g = C.&f with int f(Object) and long f(Long) is still reported, as f(Long) may be called, and so is ToIntFunction<Number> h = Math.&abs. All the candidates still count when the parameter types select none of them, or when an instance method referenced through its class takes the first parameter as its receiver. A method reference (::) is not affected.

#3134 (GROOVY-12607) includes this commit, as it depends on it.

Tests

MethodReferenceTest.testMethodPointerToOverloadsSelectedByParameterTypes fails without the change, on its assignments and return of Math.&abs and Math.&max. It also runs them and covers the overloads that must still be reported. groovy.transform.stc.* and org.codehaus.groovy.classgen.asm.sc.* pass. The Checkstyle and CodeNarc gates pass.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.3417%. Comparing base (7a317c9) to head (a95c86b).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #3250        +/-   ##
==================================================
+ Coverage     74.3385%   74.3417%   +0.0032%     
- Complexity      44310      44317         +7     
==================================================
  Files            1699       1699                
  Lines          150860     150875        +15     
  Branches        28755      28760         +5     
==================================================
+ Hits           112147     112163        +16     
+ Misses          28439      28436         -3     
- Partials        10274      10276         +2     

Files with missing lines	Coverage Δ
...roovy/transform/stc/StaticTypeCheckingVisitor.java	88.0772% <100.0000%> (+0.0368%)	⬆️

... and 13 files with indirect coverage changes

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: a95c86b
▶️ Tests: 122015 executed
⚪️ Checks: 26/26 completed

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[daniellansun]

LGTM for GROOVY-12716.

After GROOVY-12623 checked a method pointer’s return against the LUB of every overload, Math.&abs → Function<Integer,Integer> wrongly saw abs(double). Restricting the checked set to overloads the SAM parameter types can select (best match, plus narrower parameter types a subtype value may pick), and falling back to all candidates when none match or when a class-expression instance method takes the receiver as the first SAM parameter, matches run-time selection.

Tests cover abs/max positives, and the intentional ToIntFunction<Number> / ToIntFunction<Long> precision errors. CI fully green.

Merge notes: already merged into #3134’s tip — land this first, or treat #3134 as the combined landing vehicle. Related in spirit to Paul’s #3257 (functional overload choice), but this filters by parameter-type selectability for return checking, not by functional-argument arity.